(单词翻译:单击)
Thanks to Skillshare for supporting this episode, and this whole week, of SciShow.
感谢Skillshare赞助本期及本周《科学秀》。
In the tropical rainforests of South America, there's a flying animal that lives in colonies in caves,
在南非热带雨林中，有一种会飞的动物寄居在洞穴之中，
emerges at night in search for food, and navigates using echolocation. And I'm not talking about a bat.
它们出没于夜间，寻找食物，并依靠回声定位引导方向。我说的不是蝙蝠。
Believe it or not, I'm actually talking about a bird, the bizarre oilbird, known to locals as the guacharo.
不管大家信不信，我说的真的是一种鸟类，怪异的油鸱，当地人称之为guacharo
Oilbirds diverged from their closest living relatives 50 million years ago,
五千年前，油鸱背离了它们的近亲，
and in a lot of ways, they've become more like bats than other birds. They roost high up in caves, for example.
从多种方面来看，它们更像是蝙蝠而非鸟类。比如，它们栖息在高高的洞穴中。
One oilbird colony can include as many as 20,000 crow-sized birds.
一块油鸱栖息地可容乃多达两万只乌鸦大小的鸟。
And since there's not a lot of nesting material available in a cave,
由于洞穴中没有很多筑巢材料可用，
they build their funnel-shaped nests out of a mixture of regurgitated fruit and their own feces. Sounds cozy, yeah?
它们用反刍水果和自己的排泄物相混合建造漏斗形的巢穴。听起来很舒适不是？
And like a lot of nocturnal animals, including many bats, for the record, they have excellent night vision.
据记载，和很多包括蝙蝠在内的夜行动物一样，它们的夜间视觉非常好。
They accomplish that by packing their retinas with rods, the light receptors responsible for vision in dim lighting.
因为它们的视网膜和视杆细胞包裹在一起，光线接收器负责昏暗光线中的视觉。
In fact, oilbird retinas have the highest density of rods of any known vertebrate: one million of them per square millimeter.
事实上，油鸱的视网膜是所有已知脊椎动物中视杆细胞密度最高的：每平方毫米中就有一百万个。
Your retina has a max of about 150,000 rods per square millimeter.
人类的视网膜中最多只有每平方毫米约 150,000个视杆细胞。
These birds have so many rods that there's almost no room leftover for cones,
这些鸟类有这么多的视杆细胞，因此几乎没有空间留给视锥细胞，
the other light receptors, which handle visual acuity and color.
这是另一种光线接收器，负责视敏度和色彩。
That means their view of the world is probably fuzzy and dull.
这意味着它们所看的世界是模糊昏暗的。
Even the world record holder for rod density needs some light to see, though, so the birds eyes are no help in pitch black caverns.
即便是视杆细胞密度的世界纪录保持者，这种鸟类的眼睛在黑暗的洞穴中也没有帮助。
Which might be why they're the only birds that have figured out how to echolocate.
或许也因此让它们成为唯一一种知道如何使用回声定位的鸟类。
To keep from getting confused in a densely populated cave, each bird clicks at a slightly different frequency.
为了防止在密度集中的洞穴中迷失方向，每只鸟以稍微不同的频率发出滴滴声。
And unlike bats, oilbirds' clicks are audible to human ears,
和蝙蝠不同，油鸱的滴答声是人类可以听得见的，
so if you were standing in one of these caves when the birds return to rest, you'd hear quite the cacophony.
所以当鸟儿们回巢休息时，如果你正好站在其中一个洞穴前，你会听到刺耳的声音。
Oilbirds' resemblance to bats is a classic example of convergent evolution,
油鸱和蝙蝠的相似是趋同进化的典型例子，
where different animals facing similar pressures from natural selection end up with similar traits.
趋同进化是指面临自然选择中相似压力的不同动物结果会有相似的特质。
They're so bat-like, that you would think we'd call them batbirds.
它们和蝙蝠很像，会让你以为它的名字叫蝙蝠鸟。
But if you've been wondering where that name came from, yes, there's a story there.
但是如果你想知道这个名字的来源，没错，这是个有故事的名字。
Oilbird comes from the fact that their favorite food is the fatty fruit of the oil palm.
油鸱这个名字源于它们最喜欢的食物—油棕榈树的肥美果实。
Baby oilbirds in particular become so plump from their palm-rich diet
尤其是小油鸱，丰富的棕榈树果实让它们如此丰满
that indigenous people in Venezuela used to collect chicks so they could render their fat in pots to use as fuel.
以至于委内瑞拉的原住民过去常收集这些小鸟，提取它们的脂肪用作燃料。
You know, the more I think about it, the more I like batbirds instead.
想的越多，反而就越喜欢蝙蝠鸟这个名字。
Maybe it's time for, like, a rebranding. Let's try it out: Thanks, batbirds, for the reminder of just how weird nature can be!
或许是时候重新取个名字了。试一下：谢谢，蝙蝠鸟，让我们知道了自然有多么诡异！
So I know that you know bats and birds are different classes of life, but there's still a lot of differences just between species of birds.
我们都知道蝙蝠和鸟类是不同类型的生命，但是鸟类之间也是有很多不同的。
All this week we've been sharing Skillshare classes we enjoyed, and thinking about oilbirds,
本周我们将分享我们喜欢的Skillshare课堂，想起油鸱
made me curious if Skillshare offered a class on bird identification.
我就很好奇，不知道Skillshare有没有关于鸟类辨识的课程。
I found this one called The Casual Birder taught by Sue Pulsipher, and it's kind of a hidden gem on Skillshare.
我发现有一期叫做《The Casual Birder》的课程，这是Skillshare隐藏的宝藏。
It's like if David Attenborough was your sweet aunt and you took a trip to the Galapagos islands together.
就像是如果大卫·爱登堡是你甜姐，然后你们一起去加拉巴哥群岛旅行。
At first it seems pretty basic, like a flamingo and a hawk are both pretty easy to identify,
起初就很简单，比如火烈鸟和老鹰很好辨别，
but she goes into really interesting details about all the birds she talks about,
但是她很专注于所有鸟类的有趣细节，
like that bill of flamingoes and how they use it to eat upside down!
比如火烈鸟鸟喙以及它们如何使用鸟喙颠倒着吃东西！
And she shares footage of other animals you'll see while birding, like, in the Galapagos, iguanas.
当你在，比如加拉帕戈斯群岛，看鸟的时候，她还分享了其他动物的视频，
I was surprised by how charming and fun this class was,
我很惊讶，这堂课如此有趣让人着迷，
and it just goes to show that you no matter what you're looking for, you can probably find a class about it on Skillshare.
想看什么都能在Skillshare找到。
Thanks to Skillshare for supporting SciShow and for offering all SciShow viewers two months of unlimited free classes.
感谢Skillshare对《科学秀》的赞助，并为我们的观众提供两月无限免费课程。
Click the link in the description to take advantage of this offer, and support SciShow at the same time.
点击下方链接获取本次机会，同时支持《科学秀》。
And if you go birding or take Sue's class, let me know what you saw and learned in the comments.
如果你想看鸟或是上苏的课，请在评论告知大家都看到学到了什么。
